1997 Jeep Cherokee heat just stopped working

I have a 1997 jeep grand cherokee laredo, my heat worked fine up until yesterday. It just stopped working. I went to turn the knob on high to heat my jeep up and got nothing. It did that once last month but an hour later it just started working again. I tried to the blower motor and its working fine and then replaced the ac/heater blower controller and it still doesnt work. Please help me. I have a 2 years old and cant be without heat